Oversensing of atrial fibrillatory waves in a subcutaneous implantable cardioverter-defibrillator

Figure 1. A: Baseline electrocardiogram showing coarse atrial fibrillation. B: Electrocardiogram postprocedure showing sinus rhythm with biatrial hypertrophy.

Figure 2. Device interrogation showing oversensing of atrial fibrillatory waves. Four consecutive oversensed atrial fibrillatory waves (second row, decision phase) result in rate detection classification in the shock zone; after 18 of 24 events are binned, a shock is delivered. The baseline (red line) begins to shift around 6 seconds, which corresponds to initiation of oversensing. • = discard; C = charge start; N = noise; S = sense; T = tachyarrhythmia detection.

Figure 3. A: Tachycardia before the baseline shift, with SMART Pass both OFF (top) and ON (bottom). Superimposed are the sensitivity decay curves. The QRS/T-wave ratio is much higher after SMART Pass filter application, indicating less susceptibility to oversensing. Some oversensing (downward arrows) is seen without the SMART Pass filter. B: Tachycardia event after the baseline shift, with SMART Pass both OFF (top) and ON (bottom). Superimposed are the sensitivity decay curves. Atrial oversensing (downward arrows) is eliminated with the SMART Pass filter.